This is a very tiny, light-weight addon with a single purpose: answering the question "Where in my bags did that item go to?" To use it simply alt-click an item link in the chat window or type the command "/find name". Any bags, including the key-ring, containing matching items will open if needed and the icons for those items will briefly flash to show you where they are. In addition, if you are at the bank your bank bags will be searched as well.
Use the alt-click feature to find items that you just auto-looted or received in the mail. It's handy for things like disenchanting trash greens that you just picked up or stacking items mailed to a mule at the bank. The /find command is a case-insensitive substring search so just a few quick letters usually suffice. For example, typing "/find dus" should show you all stacks of Arcane Dust, Illusion Dust, etc.
Note that this addon expects the standard Blizzard bag interface and thus is likely to be incompatible with bag UI replacements.
Enjoy!